Tuesday, February 26, 2008

(IT WILL BE POURING SNOW AT MY 7 SPRINGS SKI TRIP THIS WEEKEND, AND EVEN BETTER...THE FOOT GIRLS WILL BE THERE TO ENJOY IT ALL WITH ME. )

(No, not that one. I'm talking about the GFS Fantasyland...this one:

TUE 2-26 10:30 PM. I know it's hard for you ravenous powderhounds not to get excited when you see maps like this. It's similar to how the administration gets teachers to attend faculty meetings on time, they just announce that chocolate is being served to the first 25 people who show up. You've never seen teachers move so fast after a long school day. If they consider chocolate a food group, then people like you reading this site probably consider impossibly fun computer model scenarios sweeter than pure sugar itself. Just a minute, I need to grab my evening dose.

Ok, back now. ::head twitching:: I call this the GFS FantasyLand, because it is just one model run of the US based Global Forecast System from Monday 2/25 showing some crazy scenarios for next week's storms. One idea going forward from here is that it appears increasingly likely something very significant will pound the East Coast the middle of next week. While climate indicators don't seem that promising: The NAO is strongly positive, the PNA fading to near-neutral. This is opposite of the setup we prefer: a negative NAO (trough in the East), a positive PNA (ridge in the West). Regardless, the GFS, European, Canadian, et all are all showing a major major event swinging east by next Tuesday morning that is going to be hard to avoid. Although a lot can and will change over the next 7 days leading up to arrival of this event, it is interesting to note a number of models have continued to show something brewing for the 3/4-5 period now for several days in a row, so we will keep watching.

Yes, I know, the same thing happened in March 2001... for days before, the models projected a massive Day After Tomorrow type blizzard which was going to bury the 95 corridor under 2-3 feet of snow. The hype was galactic in nature, and schools were closed all the way to the Moon. Everything was shut down from Boston to DC, even BEFORE the storm struck. It was my first year of live classroom teaching in science, and I was in Lancaster County, PA at the time. I remember just before going to bed that night, a TV forecaster from Philadelphia showed the entire viewing area under a deep blue shading with 24" - 36" plastered over it. The next morning, I awoke to 2 inches. The storm had shifted east overnight, blasting northern and central New Jersey as well as parts of New England with just some of the crippling snow that had been expected in the cities. It was and still is in the minds of many weatherfolk, the biggest bust in the history of Mid-Atlantic weather forecasting.

Monday, February 25, 2008

TUE 2-26 10:00 PM. At least your week in the Mid-Atlantic started tranquil, with sunshine and seasonable temperatures on Monday. From here it gets interesting, and much colder. On Tuesday, the vigorous cross-country system that impacted western states Sunday arrives on the East Coast with force. By afternoon, heavy windswept rain overspreads the region, with temperatures rising into the 50's on southeast winds. Overnight into Wednesday, a powerful cold front sweeps to the coast and leftover moisture may briefly change to snow before ending. Noticeable sub-freezing temperatures will arrive behind the front, creating pockets of black ice that could cause some school delays Wednesday morning in Baltimore County's Hereford Zone along with some parts of Frederick, Carroll and Harford Counties. Starting Wednesday, the region spends remainder of the week in January-like conditions, with highs in the mid 30's to near 40. The next chance for precipitation looks to be a clipper on Saturday bringing flurries or light snow.

Later this evening, I will post some basic ideas about next week, as it appears there's one or two more chances for snow during the upcoming 10 day period. I did leave some snippets about it in the previous post if you want to go look for them!

Sunday, February 24, 2008

It is very unlikely this system will trend far enough south to become a major coastal Kahuna/snowstorm. The surface Low will remain over land and not transfer energy or redevelop off the Carolinas. Regardless of that, this system will have tremendous energy and impact the northern half the country from California to the Northern Plains, Great Lakes and into New England...bringing heavy snow and significant icing across many states. This Accuweather graphic breaks down the storm evolution well. A current satellite image from the west coastshows quite a bundle of energy now moving through the Rockies.

SAT 2-23 7:00 PM. FEBRUARY FINALE IDEAS: The newest Euro and GFS (not shown here) is keeping the primary surface Low near West Virginia/PA Tuesday night. This is being closely followed by HPC as you would expect. You can follow the model animation here. Note that I don't hug just one exact model, I'm providing this as representative of the trend that's developed with our next storm between the GFS and Euro. Also of note are the trends with the NAO (risen to strongly positive) and PNA (still strongly positive but dropping sharply). Those indicate a more zonal or east west flow across the country, further limiting any chances for a big coastal storm. However, you will feel a SuperKahuna blast of cold air, and may set the stage for a Winter Finale as we head into the first week of March. For the sake of ravenous powderhounds, good ole' Mr. Margusity of Accuweather is keeping a distant eye on upcoming storms. You can also peruse the Eastern US Weather Forums on what others are saying about indicators of these storms or lack thereof. Ifyou really want to take a trip down Weather Fantasyland lane, another blogger like me has..believe it or not..created an entire site just for the purpose of tracking ONE storm. Hey now, don't knock it, because regardless of the outcome, it's fun for us crazy powderhounds simply to have a potential storm to track over a 10 day period. The site title is "Storm of the Century" and the link is: http://youhavebeenwarnedmarch5th.blogspot.com/ (note: do not click on link if you're from BCPS, it will be blocked due to the domain name.) Laugh now, while you still can.

SAT 2-23 8:00 AM.POST-STORM SYNOPSIS: The Mid-Atlantic and Northeast did experience a prolonged period of wintry/frozen precipitation as originally anticipated, but it ended up being much more intermittent than forecast, which reduced storm totals. Despite lower accumulations, what did fall was more than enough to make travel extremely hazardous for many areas during a majority of the storm period, so this time it seems the region-wide closings were better aligned toward safety than over-reaction.

Before we launch into another 5 day period of storm analysis, there needs to be a debriefing on what was originally said about the current event compared to what happened. Some of the ideas I've thought of initially are this:I believe the storm's underperformance was due in part to temperatures Thursday night 2/21 not decreasing as much as originally anticipated. Had it been 26 in Baltimore as forecasted for example instead of 29-30, I ascertain the changeover from light snow to sleet/freezing would not have occured as quickly from the city south and east, robbing snow potential. Instead, evaporative cooling from snow falling through those lower temperatures might have kept the temp down in the 20's all day, enhancing the freezing rain potential once it did arrive. Granted there are lots of other factors, but one cannot ignore the effect a 3-4 degree difference in temp would do at the onset of a storm.

The GFS and NAM computer models overall handled the precip onset well, and 48 hours out had finally settled on a reasonable solution, but appeared to have overdone the amount of liquid available. In addition, it was clear to all of us watching the radar that the two systems were not going to phase together. Knowing this, we should have better anticipated the dry slot was going to monkey wrench the forecast...as in robbing some areas of precip (say from Anne Arundel-Howard Counties west to Frederick County). The NWS did actually factor this into their forecasting, but the results made it appear the whole situation caught them by surprise, which in fact they knew and saw it with their own eyes. The Sterling VA NWS office only recorded a trace of snow, when the expectation was for 1-2 inches overnight. The same story was repeated in many of your backyards, and it appears no one in the "comments community" observed an accumulation greater than 1.5" right?

I welcome any of your post-storm analyses, (the what happened and why) and will be glad to post them here in the main site with you as the author. Our first responder is Kyle from Howard County, and his writeup appears below the storm grading section.

POST-STORM ACCURACY CHECK: A general lookback at (1) The original forecast(first issued publicly Sat 2/16) and; (2) The final call (posted below). Where was the call right on, where did it bust, and why?

FINAL ACCUMULATION SUMMARY:Time frame for these total storm projections is the originally forecasted period of Wednesday 12PM 2/20 to Friday 12 AM 2/22.

MAXIMUM PRECIP AMOUNTS: FORECAST3" along the I-95 corridor from Washington to Philadelphia. 4" in central and southern Maryland, 5" in northern Virginia, western Maryland, the WV panhandle and southeastern PA. My location of Dundalk and the nearest official reporting station, BWI, will be used to grade the prediction. I project BWI will have a total of 3" of snow/frozen precip, and Dundalk, MD will max at 4". These numbers included ice. ACTUAL: Because the original call was for totals to include Wed PM to Fri PM, that includes the clipper snow Wed afternoon. Results are listed as: -Location: Forecast / Clipper amount + 2/22 amount = total / forecast = Departure in % and Final Grade. Source was NWS Public Information Statements from my link pages.

5) Those darn mountains and mean bay: Seems like storm after storm looks good on the radar over Ohio/Tennessee until they reach the Appalachian Mts. where any storm seems to come out deformed and weaker. The bay, as Mr. Foot has mentioned, keeps on radiating heat throughout the winter, which surely didn't help our pre-storm temps.

Friday, February 22, 2008

FRI 2-22 4:00 PM. The latest Baltimore NWS forecast indicates that while the storm is not over, we are on the upside and bulk of precip has passed. Intermittent freezing rain and drizzle along with areas of fog throughout the DC and Baltimore regions may hamper the evening commute. As Capital Weather pointed out, when the sun dips, some wet less traveled areas will likely refreeze somewhat. I also am pleased to bring you a new feature and interactive feature discovered on their site. You can active it simply by clicking and scrolling.

MAXIMUM ICE AMOUNTS:(FRI PM: Obviously this entire section of the forecast busted, no one saw ice amounts exceeding 1/4" in the entire region, according to storm reports.) My projection of icing inside the numbers posted above. From Washington to Baltimore: .50" of freezing rain / .75" of sleet (includes the adjacent Metro Counties) Areas farther north and west (from Carroll County on west and north: .25" of freezing rain / .50" of sleet. From Harford County north and east to Philadelphia and it's western suburbs: .75" of freezing rain / 1" of sleet.

MAIN IMPACTS: Snow changing to sleet and then freezing rain by noon south of the PA-MD line, and over to freezing rain by nightfall north of the PA-MD line. (FRI PM: That part did generally occur, although much earlier than expected, by mid morning in many locations) Once accumulating snowfall has ended and freezing rain trends become clear, NWS will likely switch Winter Storm Warnings over to Ice Storm Warnings for much of the region. This may very well lead to one of the most paralyzing ice events of recent years for the I-95 corridor, and could surpass the Valentine's Week Disaster of 2007 at least in terms of total ice accretion. (FRI PM: Since 1/4 - 1/2 inch of ice did not materialize, neither did these predictions verify)

FRI 2-22 10:00 AM. For those of you new to the site, we have a special term in the Baltimore region which is reserved just for events like this...CLEAN SWEEP! That means all metro area county schools are closed, along with the vast majority of the private schools, and reduced schedules/liberal leave at county and state government offices in addition to many community colleges deciding to close. I learned late this morning that even brave and strong Garrett County closed, and there were delays across the Lower Eastern Shore. A similar story is being repeated from Kentucky to West Virginia, through Central and Southeastern PA and into New York/New England. In fact, every school district I've ever lived or worked in (6 of them.. PA/MD) is closed today. Unfortunately, it is not a total sweep as it appears some district offices remained open, especially Baltimore County. So a special "wish-it-could-have-been-a-Happier-Friday-for-you" message goes out to all the office workers who now have to take a vacation day if they want to stay home. There's also many commuters whom still have to brave the elements today, and I'm sure you can tell by looking out the window they are brave people indeed. Here's hoping you all can at least try to leave early, and that you make it home safe without having squeezed your knuckles off while driving.

There now, doesn't all that make you feel warm and cozy inside? Please continue to post your location and observations in the comments, especially your temp and total snow/ice thus far. I will leave all the previous posts on this storm below so you can reminisce and look back at the evolution of the forecast. When time and children needs permit, I will post a brief overview of ideas going forward into next week regarding the potential SuperKahuna. Happy Friday Everyone!

Thursday, February 21, 2008

THU 9:30 PM.The Winter Storm Warningnow in effect until 10 PM FRIDAY for Central and Western Maryland, Northern Virginia and the West Virginia panhandle probably comes as no surprise to those of you who have been following the development of this storm since last Friday. There are no changes to the forecast, because the truth has arrived : A high impact winter storm will affect the entire Northeast region Friday into Saturday, and not a soul on Earth can stop it. View the NWS spread of warnings and advisories to understand the extent of this storm already. As for the current radar, I'm sure you're noticing the "dry slot" of separation between the two storms, but that is simply an indication the two storms will not "phase" or merge together quickly. This allows the energy from both systems to slowly blend, which actually prolonges the event...and the pain for commuters. The alternative is a rapid phasing, a quick accumulation and then out to sea. That is not likely to happen.

STORM SUMMARY AND IMPACTS: An initial 1-3" of snow starting by midnight in the central Mid-Atlantic will be followed by nearly 24 hours of sleet and freezing rain to affect the entire I-95 corridor from Washington to New York City. Interior sections from Pennsylvania to England will see widespread snow possibly exceeding 6 inches. By Friday afternoon, areas affected by ice may come to a virtual standstill, even hampering the ability of emergency and utility workers to reach residents in need. If you have something important to do, get it done on Thursday, because travel on Friday for most of you will be limited to your living room, TV room and the nearest refrigerator (assuming there's power to keep it working!)

SCHOOLS, COLLEGES, OFFICES: Most schools throughout central and western Maryland, northern Virginia, West Virgina will be closed Friday, in addition to a number of colleges as well as many county, state and federal offices. Any activities, meetings or special events planned for Saturday will have to be rescheduled, so make necessary arrangements now. Those who attempt to open or hold an event will face a travel and logistical nightmare. However, conditions will improve behind the storm on Sunday, allowing roads to dry out in time for a regular school day on Monday.

BACKGROUND AND ANALYSIS:(Skip this part if you're not into the meteorology behind the forecast).The green-blue areas on the map below indicate moisture that will by 1AM Friday be running overtop an expansive dome of sub-freezing surface/lower level temperatures. The lines that bend southwest across Virginia indicate cold air damming, a classic setup for sleet and freezing rain, which may initially start as snow. Also note the 0 deg Celsius line at 5,000 feet is deep in southern Virginia, that indicates an extensive southward push of cold air. Warm air advection at or above the 5,000 foot level will intrude later Friday morning, this will be evidenced by snow changing to sleet and then eventually freezing rain by noon. This is well depicted in the NWS forecast for Baltimore as a representative location for the central Mid-Atlantic. Comparing this Wednesday night GFS projection for 1AM Friday to the current radar, it appears the precip is moving in faster than expected, but may result in just slightly higher snow totals if it starts earlier, despite your concern about the "dry slot."

THE MYSTERY OF FREEZING RAIN. Surface temperatures on Friday will start out in the 20's, and then you'll see a quick rise to 30-32 in many areas, followed by a whole day where the temp hovers just around freezing. This is a phenomenon that often occurs with freezing rain, because water turning into ice is actually a CONDENSATION process, which RELEASES heat into the atmosphere. This "latent release of heat" helps keep the temperature just around 32 or 33. But strangely enough, if slight melting begins to occur, EVAPORATION of that water from a solid back to liquid is a COOLING process, which in turn chills the surface layer just enough to stabilize the temperature. So in effect, once a freezing rain regime has setup, it just keeps on going until enough warm air aloft mixes down to the surface and provides enough warming to take the air temperature past 33. Given the depth and coverage of the cold High pressure dome that's now in charge, I doubt we'll see a change to all rain by Friday afternoon as projected by Baltimore's WJZ. It will be fun to see who is right in the end.

Justin Berk is a TV meteorologist with ABC2 News in Baltimore who operates a very worthy blog I suggest bookmarking, and since I've been a life-long fan of ABC, I can't recommend any other network anyway. For a long range glimpse of what US computer models are projecting for next week, take a peek at the GFS animation on wunderground.com. There's also the NOAA/NWS 5-day map series, and you can even see our future SuperKahuna indicated there starting Wednesday 2-27. Once we get the first Kahuna launched in full (translate: me home Friday for a day off to do the analysis), then I can start to show you data and maps for next weeks potentially major event that could make this upcoming storm look like a flurry!

Wednesday, February 20, 2008

WED 5:00 PM. I personally was glad not to see an early dismissal, as today might have been the only day this week I see my Environmental Science students. With interim quarter grades due Friday, I knew it be their last chance to lock in the grade they want. They all knew why, as the word has gotten around about Friday's storm. But then you should have seen the look on their face when I mentioned what's brewing for NEXT week! The next 10 days could turn out to be among the most exciting periods of winter weather of the decade. "What would cause that to happen?" they wondered. "Oh nothing big, really, just a massive hemispheric trough extending from the Arctic circle to the Gulf of Mexico, with a possible stalled cutoff Low parked over the East Coast..for a day or two. Kinda like March 1993. That's all. Okay, now back to the assignment that's due by the end of class." :::stunned silence deer in headlights::: Needless to say, they were motivated to get the work done.

WED EVENING DISCLAIMER: Note that at the end of class I showed them via the internet these were not my original ideas, but that of two different forecasters whom report on long range trends. I'd never have enough expertise to create that kind of dream scenario on my own...and end up being right.

DELAYS ON THURSDAY MORNING?Difficult to predict this early, depends a lot on how much more falls, if there is rapid refreezing overnight. I would definitely set the alarm, and just be pleasantly surprised (or annoyed) if there is one.

THURSDAY NIGHT-FRIDAY: There are no major changes except to make it clear I expect more ice than snow due to cold air damming at the surface.This high probability of frozen precipitation and it's arrival overnight into Friday morning makes the closing of schools and colleges a near slam dunk. A roundup of what the evening forecasters are saying will be very interesting to see, I expect a wide range of ideas.

WED 6:00 AM. With a snow advisory posted for central and western Maryland, NWS ideas on the clipper arriving this afternoon are now coming around to what has been discussed here for several days. The general thinking on this first round has been that it will be light and intermittent, and not enough to prompt early dismissal of schools. However, this is also a case of De Ja Vu all over again, because those were the original ideas on the Dec 5 "Little Storm That Could." So what's the likely situation this time? Given a reasonable radar presentation, and the fact a slightly warmer atmosphere can provide additional moisture, we cannot rule out a one hour early dismissal for schools in the Baltimore Metro area. Of course, if you see the "blues" falling apart coming over the mountains, then game over. Those of you with access to comments, please continue to post your observations and any changes you detect in the forecast.

SPECIAL NOTE TO COACHES AND ATHLETIC DIRECTORS: Even without an early dismissal, the clipper's arrival time of 1 PM - 3PM does present the possibility that afternoon and evening activities will be cancelled.

Tuesday, February 19, 2008

TUE 2/19 10:00 PM. For those of you in the school system, whether students, parents or teachers, the answer is MOST LIKELY YES. Since we are approaching the onset of this 2-3 day event, I have condensed the main ideas down to just a basic overview. If you need more detail, scroll down below this post for the analysis from this past weekend.

THE WEEK AHEAD: A clipper arrives Wednesday afternoon in the Baltimore Metro area, but most likely late enough in the day to affect evening traffic more than closing schools early. This system may produce accumulations similar to that of the Dec 5 storm which caused a 2 hour delay the next day in many school districts. There could be 1-2" across the region by early Thursday morning, prompting another round of delays. The second event will be a series of weak Low pressure systems moving toward the Mid-Atlantic from Thursday night through Saturday morning. Given that snow, sleet and freezing rain are projected starting Thursday night, it is becoming increasingly likely this will interfere with the school schedule on Friday.

THE BREAKDOWN:

WHEN? First round arrives Wednesday afternoon in the Baltimore Metro region and may produce up to 2" before departing late evening. Slick roads may cause schools delays Thursday morning. Second round moves in Thursday night and continuing through Saturday morning, total period accumulation for the DC-Baltimore Metro region by Friday morning could near 4" which includes 1/2" or more of sleet/freezing rain.

WORST PART? Well that's hard to say because it ALL looks bad for commuters. Friday morning is likely to be the most difficult travel period of the week.

HOW LONG? Majority of precipitation will exit the region by Saturday afternoon, and may even change to rain Friday afternoon before it does.

WHAT ABOUT SCHOOL? I suspect delays Thursday morning, and many schools closed Friday across the region from Virginia to Maryland to southeastern PA and New Jersey.

QUESTIONS ABOUT THE STORM SITUATION POSED BY READERS

1. Why isn't this going to be a coastal storm and give a lot of precip to the mid Atlantic?

Highly unlikely the current setup will result in a single coastal storm like Jan 22, 1987 or Dec 4-5, 2002 to name a few. Too much upper level energy spread over a large area is going to prevent any one Low pressure system from wrapping up all that energy and turning into a classic Nor'easter. The high is not projected to be in the best spot for that anyway. The best comparison could very well end up being the Valentine's Day Massacre of 2007, where some areas of the Mid-Atlantic got near equal amounts of snow AND sleet/freezing rain. There will be a lot of precip, but along I-95 and north/west of the cities, it is likely to be a kitchen sink storm.. snow over to ice and maybe even back over to snow before ending Saturday. Adding the variable of ice always cuts down on snow accumulations, but precip there will be for sure.

2. In the 03 storm the temps were becomming marginal for snow or ice and it snowed. Could it be anything like 03 and a huge suprise to everyone?

I just came across an intriguing map posted on the Eastern US Weather Forums, and I'll post it here for you to see shortly. It's all about the high. In that situation the high was clearly sliding over the Great Lakes and into southeast Canada. Not so this time, though the models are having trouble dealing with where that high is going to place Thu and Fri. Secondly, the air mass coming is cold, but not super incredibly such. I remember here in bayside Baltimore County it was 17 F and snowing teensy tiny little crystals. I had never seen such heavy snow at such temperatures in the coastal plain. The high that's coming may give us a day in the low 30's with overnights in the 20's...comparatively way warmer than the Feb 03 storm. The surprise could be in the prolonged period of icing that may develop Friday into Saturday.

3. If an arctic air mass is coming down then wouldn't that create lots of cold air damming to take place?

There is already deep concern about the cold air damming signature that's developed on some computer models for Thursday into Saturday. Even though a higher sun angle this time of year might negate some of the storm's effects by warming cloud tops, incoming solar radiation warming roads and parking lots...there is still going to be plenty of cold air to keep the ground cold. It's already arrived in force, for Monday at noon in Dundalk I observed 75 F while we were having lunch on our deck, and now at 9:30 PM it has dropped to 42 F. I think NWS offices are picking up on the potential for a major ice storm to follow the first round of snow, and you'll see this reflected in Special Weather Statements starting to fly by Wednesday morning with Winter Storm Watches posted by Wednesday night.

Monday, February 18, 2008

2 PM MON 2/18: For those who may think this site is purely for entertainment purposes only... YOU'RE RIGHT! Who doesn't love drama, conflict, uncertainty, whodunits and intrique? You can find all that and more in the weather each day. I have always deeply enjoyed the National Treasure series, doesn't the inner child in us all love a good story filled with fantastic clues leading to a wild treasure hunt? In forecasting complex storms, I believe it's the same kind of arrangement, and I've been waiting all winter to use this analogy of my favorite line from the movie. If you need a refresher, or don't get out much and have no idea what I'm talking about, then view this clip from youtube containing the first 5 minutes of the movie. After that, come back and read the brief analysis following this graphic:

Pardon the anthropomorphism, but I believe the atmosphere is revealing clues to us on what's really going to happen, and I am trying to pin them down. A well-known forecaster at Accuweather made the point earlier today of a striking similarity between what is about to happen and that of the 3 day period prior to the Feb 03 Blizzard (insert reassuring statement here that neither he nor I are forecasting a blizzard). It's quite simple. Friday night into Saturday Feb 14-15, there was front runner clipper that brought 2-4 inches to the central Mid-Atlantic, and was all done Saturday night. Most of the public who were enjoying their President's Weekend weren't paying close attention, and went to bed Sat night thinking that was it. (Including me) The clipper brought in the Arctic High, the moisture gathered from the Gulf Coast and ran right into the High. Sunday morning we awoke to what no one expected: moderate to heavy snow falling in very cold temperatures. The high departed slower than we thought it would, the easterly fetch kept pumping in Atlantic moisture added to the tremendous surge of Gulf moisture already in place, and pow! Two feet later, the rest is history. Now, given that history lesson, look over the storm synopsis from a long time reader, Mr. E.H. of Boston, and let us know what you think.

STORM 1: THE MID-WEEK CLIPPER. This first system comes in Wednesday from the Ohio Valley streaking towards Pennsylvania, Maryland and Virginia. Snow will break out from DC to north of Philly as the center of the Low passes over central VA. I would expect a heavier band of snow somewhere from BWI-PHL-SNJ. Overall, I'm thinking a quick hitting 1-3" here with a few 4" amounts embedded outside the cities. A classic 1-4" clipper despite potentially low moisture amounts to start.

Then we watch the developing second system in the southern Gulf States. A southerly flow will try to ride over a fairly substantial cold air damming in place and this will allow for overrunning snows to take the place of the departing clipper snows in the Mid-Atlantic. Some may not even notice the switch from clipper snows to overrunning snows :)

STORM 2A: MID-ATLANTIC OVERRUNNING EVENT. Snow will streak up from Tennessee toward the I-95 corridor Thursday night before turning over to rain Friday in the cities and coastal areas, while staying sleet/freezing rain just northwest of the cities, where some significant icing will take place. Before the changeover, I could still see a couple inches accumulate, bringing an accumulative snowfall from WED-FRI averaging around 3-4"

STORM 2B: INTO THE NORTHEAST (Continuation of STORM 2A, just further north) As the Mid Atlantic's major cities start to transition to rain, we will see NYC and Providence-Boston get into the action. Snow will streak into the region from the southwest as we head into Friday night and Saturday could yield a snowy day. I am not saying heavy snows, but a moderate accumulation, perhaps a 3-6" snowfall for Southern New England with maybe closer to a 4-8" snowfall north of NYC. Not a major event, but a winter event nonetheless as I bask in 60 degree warmth while writing this in Boston.

OVERVIEW: Snow Wed PM in DC-BWI-PHL-SOUTHERN NJ. Heaviest from BWI-PHL. General 1-3", isolated 4". Late Week MESS Mid Atlantic. Snow to Ice to Rain (SE). Light Snow Accumulations Possible. Significant Icing Interior. Northern PA/NY State/New England Snow Friday PM - Saturday. Moderate Accumulations Possible. (Editor's note: Much appreciation to E.H. for putting this together, he and I have seen many a storm go WAY farther north than was orginally projected, so I'm leaving the calls for southern New England there.)

THE ON-AGAIN, OFF-AGAIN STORM IS ON AGAIN

8 AM MON 2/18: Today, I won't argue with anyone who wants to label me a "model hugger" in the sense that it comes across I'm just shifting my positions based on every individual model run. I normally follow the US generated Global Forecast System (GFS) and the European (ECMWF), to get an idea of general trends. Last night both were showing total suppression of precipitation to the Carolinas for Thursday into Friday. A professional meteorologist, Mr TQ, whom occasionally comments here, has helped set me straight that we are indeed dealing with a negative NAO middle to late next week. However, it seemed that the models were also just suppressing the precipitation too far south too quickly. Regardless of what was being projected, I felt the large scale dynamics were (and still are) going to produce an over-running event. Sure enough, that's what the overnight models came out with, as shown below.

So once again, healthy skepticism that "It'll all stay south of DC" cannot be discounted. Obviously all of this still remains in the long term in meteorological terms, and in honor of Justin Berk on ABC2 News, (as well as common sense) we must remember the whole thing will change multiple times in the next 5 days. For those with a snow bias, if the models have started a northward trend of the precipitation shield, then just imagine what this might produce in come Friday morning. For Maryland and Virginia, I'll stay with a preliminary total of 4 or more inches of snow over the period Wednesday night to Friday night. We must also give equal consideration to the possibility that later in the period, snow may change over to freezing rain or sleet. Below is my contradicting post of consternation from Sunday night. I'll leave it there for comparison of last night's ideas.

THE OLD RULE NEVER FAILS:

"PREDICT THE HIGH...AND YOU PREDICT THE STORM"

SUNDAY 2/17 PM: I am providing the other side of the discussion, in the event this bears out come mid week. Above was the Sunday night GFS projection for Thursday and Friday. As you can plainly see, very little if any precip in the Mid-Atlantic for that period. Except for the yellow mark over Baltimore that'll represent egg on my face if there's no storm. The strong 1040 mb high coming behind the current storm moving through the Great Lakes looks to charge southeast according to many models. (That was the overall thinking Sunday night).

SUN 2/17 AM: This is a Foot's Forecast Alert. Although computer models continue to conflict and alternate in their projections, there will be a major winter weather event of some kind in the Ohio Valley and Mid-Atlantic from Thursday into Saturday. This post will be revised over the next several days, with an continually updated overview for those who just want the basics. Below that will be the on-going, full-blown more-than-you-could-ever-want-to-know analysis. The most important headline going forward is that this WILL BE A LONG DURATION MIXED PRECIPITATION EVENT POSSIBLY LASTING 2 DAYS OR MORE, so let's just hope it does not end up as an ice storm. Anyone remember February 1994? Figured not, you probably blocked it out.

STORM OVERVIEW:This outline will be revised as information and indicators change, but it represents my present thinking for the Mid-Atlantic states for central VA - Maryland - central PA to New Jersey.

WHEN? Arriving in MD and VA Thursday between 3PM and 9PM. Starts light and intermittent, increases in intensity but will alternate between light and heavy due to waves of low pressure moving along a frontal boundary.

HOW LONG? Majority of precipitation will exit the region by Friday night.

WORST PART? Overnight Thursday until Friday afternoon.

HOW MUCH? If precip remains all snow ANDif it trends more north than models currently indicate...then 4 or more inches for central/northern Maryland, central/northern Virginia (4 or more in a 12 hours is NWS Criteria for Heavy Snow) If freezing elements mix in, snow amounts will be cut down closer to 2" and sleet/freezing rain could account for at least 1/2"

SCHOOL? Given the current timing ideas, I would project many schools in the affected areas of Maryland and Virginia closed Friday. An earlier arrival time could interfere with Thursday.

The CNBC Fast Money Summary: Both the GFS and European models as well as others, are showing various, albeit conflicting, scenarios of an Arctic High sliding into the Great Lakes/southeast Canada region by next Thursday night. This would bring noticeably cold upper level temperatures to the Ohio Valley and Mid-Atlantic. the same time a Low developing in the Southern Plains and Tennessee Valley looks to incorporate considerable Gulf and Atlantic moisture ahead of the storm as it moves toward the Eastern seaboard. The main point is this storm could go either way...an all out snowstorm given the right timing, or a more complicated snow to ice to rain storm like we saw last Feb and last week. You can be sure of this, something big (and wicked) this way comes for next weekend, and those with travel or social plans need to monitor the forecast closely. By Wednesday, weather agencies should have a better handle on the system and I expect Special Weather Statements to start rolling by then if not by Tuesday.

Note: Will be adding a revised surface map to show differences in model projections from this past Friday to today, so we have something from which to base our discussions.

ANALYZING STORM INDICATORS

1. THE NORTH ATLANTIC OSCILLATION:Currently slightly negative, but trending positive over the next few days. While not the best arrangement, if it turns back toward neutral, that might indicate the Arctic High would be at least prevented from sliding east too quickly next Thursday-Friday. Remember the ideal position for an East Coast snow event would be a high parked in southeast Canada with cold air funneling down east side of the Appalachians. SUN PM ideas: Before we go further, I have been analyzing the NAO situation more closely and something just seems out of place. Review my graphic and let me know what you think, does anyone have an explanation for the issues I present here:

NAO Indications prior to February 2003 Blizzard: Although the NAO was slightly NEGATIVE and trending toward neutral, this slight drift occured in the 2 day period just before and THEN during the storm. My theory is that was a major factor which enabled the primary Low and it’s moisture to “over-run” the High toward the Mid-Atlantic. A strong negative trend in the NAO means Arctic air will overwhelm the region and keep storms south or out to sea. PLEASE NOTE I AM NOT SAYING THIS STORM WILL RESEMBLE FEB 03, I am saying the early indicators are somewhat similar to what was seen prior to that storm and I am showing you those for discussion purposes.

Also of note is that the NAO during Winter 2002-03 spent most of the time neutral to negative, but not significantly so. In recent years, very strongly negative NAOs over several weeks correlated to extensive cold periods, and strongly positive NAOs led to unseasonal warmth. You can see from the chart below that this winter we have not even observed a standard deviation beyond 2, and winter for the Mid-Atlantic has been relatively quiet in comparison to years like 02-03 or 05-06.

2. SEA SURFACE TEMPERATURE ANOMALIES: THE CANARY IN THE COALMINE?

3. UPPER-AIR TEMPERATURE PROJECTIONS: COLDER DAYS ARE COMING UP

Below is the 850 millibar GFS Ensemble map for the Northern Hemisphere, produced 2/16 for 2/21. It clearly shows a 4 to 10 C degree negative departure at the boundary layer (5,000 foot level) over the entire Mid-Atlantic and Northeast starting Thursday, indicating that a cold and expansive High will be parked somewhere nearby. What significant is the "ensemble" is not one single computer model but a compilation of all the different algorithmic scenarios that computer has projected, and merged into a single "averaged" solution. If the average solution is noticeably below normal temperatures right at the onset of our storm, then a lot of forecasts for rain could bust big. Just think...if at 5,000 feet above Baltimore next Wednesday night the temp is already 6 to 8 degrees C below normal, if that ends up being around -15 F at those levels, it would favor the development of dentritic snow crystals. Those are the fastest to form with the highest fluff factor, and lead to high accumulation rates as was observed in February 2003. Too soon to say if that would happen, but the temperatures at least look good so far.

THE BLIZZARD OF 2003: 5 YEAR ANNIVERSARY. For a trip down memory lane, review this article in Wikipedia about the Great North American Blizzard of February 2003, which started 5 years ago, right about now. If you have extra time, take a look at this slideshow I have on an old webshots site from the storm, it makes me feel like I'm still there. Enjoy the memories, I wonder when we'll get to make some new ones like this.

Wednesday, February 13, 2008

Well, a year ago today, those of you in the Mid-Atlantic were fighting a massive ice storm that would eventually grip the entire Northeast over 3 days. Many schools dismissed 2-3 hours early, had the 14th off followed by a delay on the 15th. Are we set for a repeat? Consider the factors stacking up for tomorrow:

1. The NWS Digital Forecast Database above indicates all liquid precip will change back to snow or sleet overnight as sub-freezing temperatures return. While intermittent overall, this will make for slippery travel conditions throughout the night.

2. With dewpoints remaining high and plenty of moisture remaining on the surface, it is likely the Mid-Atlantic region will experience significant re-icing of roads leading up to the morning commute.

3. A developing low in the Carolinas will begin to pull cold air south, already evidenced by winds backing north and northwest. This secondary Low is going to inject moisture pulled from the ocean and direct it over central and eastern Maryland, just as the cold air arrives.

4. The result may be several hours of snow bursts late tonight and early tomorrow morning, with "banding" setting up on the western edge of the precip shield as the secondary Low moves northeast. NWS is going conservative, with snow amounts up to 1/2 inch, while Justin Berk of ABC2 News is alluding to the potential for up to 2" and possibly more if we see the banding develop as he indicated. Read over this Special Weather Statement in which the NWS outlines their concerns for what is to come over the next 12 hours for the DC-Baltimore region and Coastal Mid-Atlantic in general.

This will definitely be another "Nowcast" storm so I suggest you bookmark your favorite regional radar, and keep an eye on surface temperatures. My early call for Thursday schools is simple: Widespread 2 hour delays, with careful re-evaluation at 6:45 AM. If snow bands are continuing to redevelop and have overspread the area farther west than anticipated, it is even possible some districts in central and eastern Maryland will be forced to close. The other possibility is that the secondary Low might veer farther east and take the precip with it, shutting off any real chance for snow west of the Bay. Proof of that outcome will be a big dry slot forming where we thought precip would be, if you see that, you're going in on time because the winds will help to dry roads and parking lots before temps dip below freezing. We shall watch what happens with great anticipation, and I hope you'll post your observations into the evening as we see what the players begin to do.

I say that because old time teachers (and weather enthusiasts with a good memory for such things) have told me these kinds of situations used to happen a lot "back in the day." Mrs. Wrenn, a recently retired librarian from my school and a kindred spirit, could recount time after time how districts back then would be opening on time, only to have snow or ice coming down heavy. As the buses arrived at school, they would be told to turn around and take everyone back. There were other times back before the mass media culture of today, when some districts had initially announced a closing, only to change it to delayed or even opening on time. If any of you can recall those situations, it would be fun to hear about what went down. I never experienced that kind of confusion as a kid in school. The closest we ever came to that in suburban Philadelphia was the February 11, 1983 blizzard, incidentally which was a quick 25 years ago this past Monday. That morning, my Mom said, "Well, school is closed." There had been virtually no snow all winter where I lived, and nothing was on the ground. Sure enough as she told me the news, flurries began. Twenty-four hours later, we had at least 2 feet. That single event was the catalyst which launched my weather addiction, uh, er, interest and as you see it continues to this day.

SO WHAT HAPPENED WITH THE LATE CALLS? Except for school staff, many of whom have to drive considerable distances, and parents who now have to do a switcheroo loop-de-loop on their plan for today...I'm sure students are quite happy with the outcome. If you're mad or confused about how this unfolded, here's my theory: When county assessment teams performed their roundup this morning, it seemed reasonable to expect that mostly parking lots and sidewalks would be problematic, but main roads, side streets would be fine. I'll bet when drivers reported to their buses, they discovered melting icicles and a generally improving situation. Given the normal daily flow of traffic, and slowly rising air temps, just the movement of vehicles would help warm pavements. So between 7:00 and 7:30.. buses started rolling. My hypothesis on the deciding factor is that once buses got out into areas not as frequently traveled, back roads, back streets, they started running into much more slippery conditions than were anticipated. I'll bet buses began radioing back to their base station, and the chorus got loud enough that it rose to the decision-makers, which pulled the plug.

Mind you I'm not criticizing the decision, but I am confident that counties did not just randomly decide to wait until 7:30 and then announce a closing. Conditions on the ground apparently had not improved enough, and perhaps air temperatures are not rising as quickly as expected. So as the previous post headlines: Uncertainty did in fact win this time.

For those who don't read the comments, or can't find them..I pulled out some snippets from the previous post for you to enjoy here. Thank you to everyone for supporting the website and posting your observations and reflections. It has been a great 4 years thus far, and I'm sure we'll get to relish in one good snowstorm before the winter is out.

Stephanie said...

I've been reading your blog since last winter and I have enjoyed your take on our unpredictable local weather!I do have to add in a report from Columbia/Howard - I'll be really surprised if schools are just delayed tomorrow. I commute from DC and it took me about 30 minutes to clear the ice off of my car after skating across the parking lot at the train station.We had a nice sheet of ice everywhere at 6-7pm and it rained steadily until at least 9pm. It may have stopped now, I can't tell, but my sidewalk looks even more icy than it was a few hours ago.February 12, 2008 10:16 PM

Christopher said...Here's hoping PSU cancels classes tomorrow! 2 of my 4 I would LOVE to miss!!February 12, 2008 10:46 PMProspero said...Still around 30 here in White Marsh, and the precip just keeps coming. What is it about this week?Russ: I hope you don't lose water (or electricity).Maybe tomorrow we'll get that magic day.February 12, 2008 10:47 PMMr.S said...AA county Severn at 1130pm - icy as heck!! Our trex deck is a skating rink and all brick and power lines covered . Streets just look wet and we have heard the plows with salt . Hate to say I think it may only be a delay for tomorrow ! Here is to hoping I am wrong !Mr SFebruary 12, 2008 11:42 PMms abbe said...I've been reading your blog for 3 years now and have also enjoyed it. :) 5:00am and Baltimore County was the first to announce a 2 hour delay! But I hear people sliding around on the roads outside up here in Abingdon. Interesting that even government offices are opening late. Still a possibility for a closing??February 13, 2008 5:06 AMbell86 said...Baltimore County closed...back to bed.February 13, 2008 7:37 AMDave said...Hello, Mr. Foot.I have spent around two years browsing your blog and checking it nearly daily during the winter months, hoping for even the slightest mention of a delay, closing, snow, ice, or anything else in the Baltimore County area that could lead to me sleeping in.I have decided to make use of the time off to sign up and thank you for giving us a knowledgable and concise yet understandable and basic report of what we can expect in terms of weather.I would also like to congratulate you on correctly predicting the closing and delays of many schools in the surrounding regions.I think that is enough of an introduction for now.Incase anybody missed it, Baltimore County and a few others areas decided to close, thankfully.February 13, 2008 7:44 AMsnow lover said...mr foot what is up with the snow that is forecasted for tonight.February 13, 2008 7:44 AMMrs. Burke said...Fantastic, Harford County follow suit with Baltimore. Let's make it like last year, have off tomorrow, and a delay on Friday . . . that would be awesome. Better yet, off on Friday too so I can leave for my president's day vacation to Luray early!!! The trees are looking mighty bogged down with ice here in Nottingham! It looks like it is raining out there. Also - my husband even has a delayed opening this morning. That should tell you something, because JHU APL hasn't done that since this time last year! Happy sleeping late everyone!February 13, 2008 7:51 AMphotofreak65 said...Yeah! We closed. Of course the change was made just as I had awakened my high schooler (she would get on the bus @8:30 in a 2 hr delay) I told her to go back to bed - we are closed. she said, "goodnight". It is an icy mess out there. It's 32 degrees right now. The trees and grass are just beautiful. I want to venture out with the camera, but I'm afaid I'll kill myself - plus it's raining hard. Mr. Foot this is a great site. A friend of yours introduced me to this site last year and I've been hooked ever since. This storm is my first comments though. Ok now this day off officially makes Balto Co have 2 days off and 2 hours. But this is built into the calendar. Keep up the good work! I enjoy reading this.February 13, 2008 8:05 AMNeedaSnowday said...Heya Mr Foot... home safely from ORLANDO, where it was just glorious! And, just like last year... A DAY OFF to rest!! Must be Disney Magic!! :)February 13, 2008 8:22 AMMr.S said...Well Mr. Foot, you were right! I didn't expect this. My only comments are that AA County was open on time, but AA Gov Offices are closed and on Liberal Leave. There is the confusion between living in one county and working in another! I was up and dressed, and almost ready to leave when I heard the delay got changed to a closing. Well here's to a shortened work week! See you on Thursday. On a side note, sorry to the student from Calvert Hall, noticed no closing/delay for them.February 13, 2008 8:27 AMMr. Foot said...How weird is this? Welcome back to the 1960's I guess. Thanks for all the nice remarks. I'm going to put your comments in a little followup post. I have a theory on how this came about, so don't go blaming your county systems for a late call. Check back in a few for a quick post on this up above.Side note: I arrived at my children's daycare at 8:15 and they handed me the phone.. school's closed. My first thought was, "so this is what it was like in the 60's." I have been told all kinds of horror stories of schools being open on time, then suddenly closing when the buses were arriving, and even the reverse of that. In fact a few of you may even know those stories, except for Julee...that would have been before her time, (tee hee hee).

WED 2/13 7:15 AM: That was quite a not so "n-ice" surprise. As all of us in areas affected by ice have discovered, quite possibly the most miserable conditions I think are when you have a glaze of ice with water on top. What could be more grueling early in the morning than to scrap ice off your vehicle in pouring rain? That sure was a blast. But thankfully nearly all area schools provided extra time to pull it together this morning, except of course for Anne "What-in-the-heck-is-an-Ice-Storm-Warning?" Arundel County. If you have time, consider letting us know in the comments how your commute turned out, I'm curious to know just how slippery if was on side streets and the like. As for this evening's snow burst, uncertainty continues to rule the future as some refreezing of standing water seems likely, followed by a dusting of snow on top. I could see this turning into another round of delays Thursday morning.

TUE 2/12 10:00 pm: The Ice Storm Warning will be in effect until 7AM Wednesday, and there is potential for .25" to .50" of ice accretion on untreated surfaces. Even if temperatures warm above 32, school districts have to make the call at 5 AM and conditions are likely to be as bad as they are currently. I've reviewed regional temperatures, and the surface and boundary layer cold air seems well entrenched.

The extent of this Ice Storm Warning is a telling indicator that everyone, from the pros to the amateurs, underestimated the staying power of low level cold air. Almost inexplicably so, the warm air aloft has not been able to mix to surface levels as quickly as everyone believed it would. Almost as if the weather remembered what it was doing a year ago today (ice storm, ahem) and just pulled out those old programs and ran them again.

WHAT DOES THIS MEAN FOR SCHOOLS WEDNESDAY? I'm going to go out on a limb here and say the range of uncertainty is too large to ignore. Think about how quickly this surprised us all. Now let's consider Wednesday morning. Suppose your county roads have improved enough to allow for smooth traffic, but sidewalks and parking lots are still ice covered. Perhaps a delay would be the best route, give 2 more hours for air temperatures to warm enough that melting will take care of the problem for you. However, uncertainty calls that decision into question because a second storm system developing Wednesday is likely to turn any remaining precipitation back over to snow. You'd be in the very unforgiving position of having called a delay, followed by an early dismissal. The NWS has already hinted in discussions that another advisory may be needed starting tomorrow afternoon. If you throw in the potential for power outages, roads and bus routes blocked due to downed trees and branches, and slick conditions hampering road crews the opporunity to clear those areas...

Let me know what you think in the comments, make sure you vote (in my poll) since it's still the Potomac Primary, and include your observations especially status of ice on your powerlines. Most of all, everyone be safe, I don't want to see your name next to "Breaking News: Weather enthusiast electrocuted while taking pictures in ice storm."

If the question is: "When will Maryland observe the next plowable snowfall?"

The answer: not before February 16 for the I-95 corridor, with the first chance over President's Weekend, followed by another opportunity between the 22nd and 28th.

TUE 2/12 INSERT: The latest expansion of the NWS Winter Weather Advisory may raise hopes of school delays on Wednesday, but that probability will not be known until 5AM tomorrow when we see what temperatures end up...whether they rise overnight or not. Regardless of the outcome, I'm sure the uncertainty will prompt many of you to spend the evening speculating on it. Rest assured, I'll be right there with you, speculating away myself.

How will we know: Once the North Atlantic Oscillation (NAO) turns negative AND the Pacific-North American Index (PNA) turns positive, there is an opportunity for the right combination of air masses and many other factors to deliver a traditional mid- to late-February storm. However as you know a lot has to happen in the right order. One promising sign that winter will strike back in the Eastern U.S. is that interior temperatures in Alaska of late have been near -70 F. While it may seem a real stretch to connect remote Alaskan cold to a mid-Atlantic snowstorm, it is not in dispute that this cold air will make it's way south eventually.

The main culprit behind such a lack-luster winter has been the extremely strong La Nina, with water temperatures in the Equatorial Pacific running 2 or more degrees below normal C across large areas. This influences the development of a persistent high in the northern Pacific. The end result creates an overall unfavorable environment on the U.S. East Coast for big and frequent snowstorms like was seen in the winter of 2002-03 when a weak El Nino was observed instead. I'll post some graphics of these two ideas, because the differences in water temperature anomalies between this winter and 02-03 are quite revealing, and help explain a lot behind what drives certain types of winters. In conclusion, I do believe the Mid-Atlantic will see a 6" snow event sometime between February 20 and March 5, but beyond that the chances of a good snow will all but disappear as increasing sun angle begins to influence our regional climate once again.